The present invention relates to a rotatable centering spindle for centering a yarn having a central peripheral groove into which open threaded grooves run together oppositely from both sides.
It is known to provide a centering spindle of this kind on open-end spinning machines. The spindle can be lowered onto the yarn extending from the bobbin to the mouth of a suction tube and is driven at the same time in a direction such that the opposed threaded grooves forward the yarn, independently of its initial position, into the central peripheral groove. In this position, the yarn is located in such a position that it is grasped by a pivotable feeder and can be fed to an auxiliary roll pair of a piecing-up carriage. The yarn must be held back by a roll located in the immediate neighborhood of the centering spindle so that the centering spindle can be lifted from the yarn after completed centering of the yarn and its being taken over by the auxiliary roll pair. Otherwise the danger that the yarn could again be entrained when the centering spindle executes a pivoting-away motion would exist because of the potentially oblique course of the yarn towards the centering spindle, whereby yarn breaks and the like could arise.
The object of the present invention is to construct a centering spindle of the kind stated such that after completed centering of the yarn its certain release is insured in a simple manner.